Cornell University's Catherwood Library has a great Labor Studies guide with many additional resources.
Businesses in the U.S. are categorized by the North American Industry Classification System (NAICS) in order to collect statistical data about the economy. NAICS can be between 2 and 6 digits, becoming more specific the longer they are: 2 digits is the broad sector while 6 digits is an industry subsector. For instance, 56 = Administrative and Support and Waste Management and Remediation Services, 5616 = Investigation and Security Services, and 561612 = Security Guards and Patrol Services.
The New York City Department of Consumer and Worker Protection (DCWP) "protects and enhances the daily economic lives of New Yorkers to create thriving communities, with responsibilities that include licensing certain business and protecting workers' rights. The New York State Department of Labor is the state agency that enforces labor law and administers unemployment benefits.
The U.S. Bureau of Labor Statistics, part of the U.S. Department of Labor, collects, analyzes, and shares data on the labor and economy, including employment, prices, and working conditions. The BLS website is a (complex) trove of data and information, but these are some popular sources: